1. Field of the Invention
The invention relates to a solid sorption heat pump and a heating system with a solid sorption heat pump.
2. Description of the Related Art
It is known to use thermally driven heat pumps on the basis of solid sorption for heating and cooling purposes. Conventional pairs of working materials (namely sorption material and adsorbate) are zeolite and water for example, with the water as the working gas being operated in the low-pressure range. Adsorption heat pumps with such a pair of working materials have been disclosed for example in DE 199 61 629 and DE 100 38 636.
Pairs of working materials have become known which are operated in the high-pressure range. Examples are salt ammines/ammonia, as are disclosed in the U.S. Pat. No. 4,694,659 for example.
Different technical requirements are placed on solid absorption heat pumps. Especially relevant are the demands for a high heat ratio, a high power density and a simple controllability of the heat emission. The heat ratio of the available heat to the drive heat (also known as COP: Coefficient of Performance) depends essentially on the shares of the sorptive and the sensitive heat transformation during a heat pump cycle. Sorptive transformation shall be understood as the release of the sorption heat arising during the adsorption of the working gas or the absorption of the sorption heat required for desorption, whereas the sensitive heat transformation describes the energy transformation occurring during the heating or cooling of the entire system.
If one assumes ideally that the sensitive heat is negligibly small, the maximum possible heat ratio will be achieved with a certain pair of working materials. For silica gel/water this is typically at approximately 180% for a single-state heat pump. This percentage rate is composed of 100% of available heat which is gained from the drive heat, with simultaneous complete desorption of the adsorbate. The second share of 80% can be emitted in form of available heat, in the subsequent cooling of the adsorber and the adsorption of the adsorbate in the sorption material.
In order to achieve especially high heat ratios, systems were developed which became more and more sophisticated in a thermodynamic respect. The highest possible heat recovery which improves the ratio between sorptive and sensitive transformation is desired especially by arranging a plurality of adsorbers or desorbers which are flowed through successively by the heat transfer medium and are switched in a plurality of cycles. The disadvantageous aspect in these systems are the considerable technical effort, the susceptibility to malfunctions and the high production and maintenance costs.
The published application DE 199 02 695 A1 shows a sorption heat pump in which an adsorber/desorber heat pump is arranged together with an evaporator and a condenser in a common vacuum-tight container, which are all integrated in an evaporator/condenser heat exchanger.